textproduct: Rapid City

KEY MESSAGES

- Marginal to slight (1-2 out of 5) risk of severe thunderstorms this afternoon and evening primarily for damaging winds, but large hail may also occur. - Hot weather will continue through the weekend with daily chances for active thunderstorms as ridge-riders rotate through the northern Plains

DISCUSSION

(This Afternoon Through Sunday) Issued at 1048 AM MDT Mon Jul 27 2026

16z surface analysis had a low over northeastern WY with a couple of troughs; one south into CO and another east into eastern SD. Sustained east/southeast flow over western SD bringing increasing moisture to the area. Water vapour loop has upper ridge centered over NM with ridge axis into the northern Plains. Shortwave evident over northwest WY, ready to overtop the ridge and cross the CWA during peak insolation this afternoon/evening. That will be the main short term concern.

This afternoon/tonight, 1-2KJ/kg SBCAPE develops along the aforementioned boundaries with similar amounts of DCAPE. Effective shear forecast to be 30-45kts as shortwave crosses. CAMs show convective initiation by 20z, focused on the higher terrain initially and then the surface boundaries as SBCIN erodes. Clusters of storms will move east, potentially with congealing cold pools, increasing the damaging wind threat. CAMs show a couple clusters of enhanced wind gusts. Thunderstorms end overnight. Temperatures will be near guidance, but below heat headline criteria.

Tuesday looks less active right now given shortwave ridging and lack of a distinct shortwave moving through the area, but would still expect some convection tied to the terrain. Wednesday, ensemble guidance shows another distinct wave moving across the area during peak heating resulting in an elevated risk of severe weather. Temperatures remain hot, but below heat headlines criteria.

The rest of the forecast will be dominated by the upper ridge over the central CONUS and hot weather. There will be waves kicking off a few storms from time-to-time. If you believe the long term ensemble guidance, someone of a cooldown may develop next week, but confidence low.

AVIATION

(For the 12Z TAFS Through 12Z Tuesday Morning) Issued At 512 AM MDT Mon Jul 27 2026

VFR conditions generally expected through the forecast period. Wildfire smoke will continue to drift south into the region today, mainly impacting northwestern SD and the central SD plains, however smoke is not expected to impact visibilities too much. More thunderstorms are expected to develop across northeast WY around 22Z and move into western SD during the late afternoon and early evening hours. Gusty and erratic winds and LCL MVFR conditions will be associated with any thunderstorms.

FIRE WEATHER

Issued At 1048 AM MDT Mon Jul 27 2026

Elevated fire weather conditions are expected much of this week due to hot temperatures as well as minimum relative humidity in the teens and 20s at times. The joint probability of MinRH <15% and winds >25mph low at this point. The cores of thunderstorms that occur this week should contain wetting rain, but lightning strikes outside of the cores as well as strong, erratic winds may create opportunities for new fires.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.